Glaucomatous visual field loss often comes asymmetrically between two eyes. As clinical tests of vision loss are usually performed on each eye separately, a way of predicting the binocular visual field from monocular visual fields is useful. While previous studies tested binocular integration models using light sensitivity (Nelson-Quigg et al., 2000), it remains unclear how this combination affects everyday visual tasks, such as reading. The purpose of this study is to determine the best model for predicting binocular visual field integration for letter recognition, the building blocks for reading. The binocular summation properties were tested by comparing contrast thresholds for letter recognition under three viewing conditions: monocular viewing with either eye, and binocular viewing. Subjects, with glaucoma or normal vision, identified alphabet letters at thirteen predetermined locations across the visual field subtending 25 degrees visual angle. The target letter was presented at an intended retina location using a gaze-contingent display paradigm. Using monocular data, the binocular visual field sensitivity was predicted using three models: i) Best Eye; ii) Best Location, using the location with highest sensitivity for each eye; and iii) Quadratic Summation. The differences (Mean Squared Errors) between predicted and actual binocular fields were calculated to evaluate the best model. Our results showed that, for normal vision, Quadratic Summation best describes the binocular summation property of letter recognition in both the fovea and the periphery. Similarly, for glaucomatous vision, in unaffected retinal locations, Quadratic Summation (MSE=8.02) is superior to Best Eye (MSE=20.50) and Best Location (MSE=17.60). However, in affected retinal locations, Best Eye (MSE=3.28) or Best Location (MSE=3.38) is more accurate than Quadratic Summation (MSE=5.32). Our results suggest a dual-approach to binocular visual field integration for glaucomatous vision. Our findings further suggest that this dual-approach may be useful for understanding everyday binocular function, such as reading, in glaucoma patients.